1. Field of the Invention:
The present invention relates to conversion kits for truck cabs, and more particularly, to a conversion kit for converting a modular truck sleeper/cab into a day cab. A modular truck sleeper/cab is defined as a sleeper truck cab joined to a modular sleeper.
2. Description of the Related Art:
Over-the-road, or long-haul, trucks are often equipped with sleeper cabs. Sleeper cabs allow truck drivers who are on the road for several days at a time to take breaks at appropriate times. After long-haul trucks have served their useful lives on long hauls, they may be resold.
Demand for used short haul delivery trucks, or day trucks, tends to be more robust than that for used long-haul trucks. Prices for used day trucks consequently tend to be higher than prices for used long-haul trucks, other things being equal. The drivers of day trucks rarely spend more than one day driving them, so a sleeper may not be particularly useful to them. Day trucks thus generally have only xe2x80x98day cabsxe2x80x99, without a sleeper. Thus it may be desirable to be able to remove a sleeper from a long haul truck before the truck is resold, to take advantage of the potentially higher resale demand.
The design of the cab and sleeper influences the ease with which such long haul trucks may be converted to day trucks. Sleepers may be designed to be an integral part of the cab, or they may be designed to be added to the cab while the truck is assembled. If the sleeper is an integral part of the cab, it may be more difficult to remove when the truck is to be resold than, e.g. a modular sleeper/cab design.
Sleepers that are designed to be added to a cab during assembly or after sale are called xe2x80x98modularxe2x80x99 sleepers. An interface between a sleeper truck cab and a modular sleeper may present a weak point in such a structure. An integral sleeper, on the other hand, may be potentially stiffer than a comparable modular sleeper/cab design.
The potentially greater stiffness of an integral sleeper relative to a modular sleeper arises from the opportunity to design the cab and sleeper together as a unibody or monocoque structure, or to incorporate structural members such as risers, stringers, or frames that connect the sleeper to the cab. These structural members may cross the interface between the cab and the sleeper, transmitting loads from one to the other. There may thus be substantially no interface between the cab and the sleeper with respect to stiffness and rigidity.
Modular sleepers, in contrast, are generally attached to the rear of a separate cab. Modular sleepers offer the advantage of being able to be interchanged to suit various needs for different sizes and styles of sleepers in the marketplace. The ability to attach various sleepers to a cab, however, requires a common interface between the cab and the different sleepers.
In current engineering practice, a modular sleeper cab design may be a system comprised of a sleeper cab, a sleeper and a frame of a truck. The sleeper cab, sleeper, and truck frame are customarily interdependent upon each other to maintain structural integrity of the finished unit. Removal of the sleeper results in an incomplete system and hence the structural integrity of the system may no longer be maintained.
Modular truck sleeper cabs may be converted to day cabs by removing the modular sleeper and covering the resulting opening with a closeoff panel. Removing the sleeper leaves an opening in the rear of the cab formed by the rear sill, the walls, including the B-pillars, and the roof. The opening may be roughly square, and hence an incomplete system cab may be relatively weak in some modes.
Such a structure may not protect an occupant very well in the event of a crash. Such a structure may also vibrate in response to forcing functions such as, e.g. the engine""s combustion sequences and road inputs, such as tire forces. The vibration may then be transmitted to the driver without impedance. Excessive vibration can result in driver fatigue, a loss of driver awareness, and potentially greater risks of accidents.
Vibration may be characterized by repetitive reversals of motion on the part of a structure. The higher a frequency of vibration, the greater the number of reversals per unit time. A structure may be reinforced to reduce its response to vibration.
Reinforcements add mass as well as stiffness. Since the inertia associated with added mass resists changes in direction, masses tend to behave like low-pass filters for vibration. That is, a mass tends to transmit low-frequency vibration while impeding higher frequencies. Stiffness, on the other hand, acts like a high-pass filter, impeding lower frequencies and transmitting higher frequencies.
Reinforcements can, therefore, be designed to ameliorate the particular frequencies of vibrations a cab and closeoff panel are likely to experience. Combustion and road inputs, e.g. have relatively low frequencies. The frequency at which combustion events occur in a four-cycle, six-cylinder engine running at 2000 rpm e.g., is only about 100 Hz. Reinforcements to truck cabs should therefore be designed to add proportionately more stiffness than mass.
Reinforcements that aren""t optimized for the particular frequencies a structure is likely to experience, on the other hand, may add mass unnecessarily. Reinforcements that, e.g. add more mass than stiffness in an environment characterized by low frequency vibration are less than optimal. Adding weight without a commensurate gain in stiffness also reduces fuel economy and drivability. It would be desirable if reinforcements applied to a day cab conversion were optimized to add maximum stiffness without increasing unduly the mass of the vehicle.
Since day cabs are shorter than cabs with sleepers, whether integral or modular, those produced originally as day cabs, without an opening in back, are often stiffer than either. Even though closeoff panels may be bolted or riveted to the perimeter of the opening to convert the modular truck sleeper cab to a day cab, such closeoff panels have not heretofore offered structural rigidity equal to a truck cab that was built originally as a day cab, or to trucks where the sleeper cab, sleeper and frame were part of an interdependent system. It would be desirable if a converted day cab could have stiffness and rigidity comparable to a day cab produced originally as a day cab.
Furthermore, the truck manufacturer may be able to predict, e.g., that a significant portion of modular truck sleeper/cabs that were sold originally with modular sleepers attached will eventually be converted to day cabs. This presents an opportunity for the designer of a modular truck sleeper/cab to design a closeoff panel to fit their particular sleeper truck cab, along with an array of modular sleepers. This would allow the closeoff panel to be optimized for the particular sleeper truck cab. This would also allow a designer to plan a closeoff panel to take advantage of the existing fastener scheme, dispensing with the need to drill any new holes, or keeping new holes to an absolute minimum.
The interior of such a closeoff panel could also be trimmed to fit and match the truck cab, resulting in a converted day cab that had the appearance of a conventional day cab. This would make the converted day cab more attractive, potentially raising the value of the truck, since attractive, presentable products may be more desirable than unattractive, slovenly ones. It would be desirable, therefore, for a sleeper truck cab conversion kit to be designed and optimized with the sleeper truck cab and modular sleeper themselves.
Reinforcing the closeoff panel has, in the past, meant securing the closeoff panel with respect to the opening. The reinforcement members were directed primarily toward, e.g. keeping the closeoff panel flat, or simply as a method of attachment. Such reinforcements thus generally took the shape of, e.g. gussets that did little to carry loads from the closeoff panel to the day cab itself, or to the vehicle frame. Furthermore, gussets are, by their nature, added at the corners of the opening in the rear of the cab.
Gussets may consequently add mass at the perimeter of the closeoff panel without adding much stiffness, potentially exacerbating vibration in the manner of a dipole. It would be desirable if the closeoff panels were reinforced in a manner that made the closeoff panel an integral structural part of the day cab conversion. Such reinforcements may, e.g. distribute loads from the closeoff panel to the rest of the day cab and the vehicle frame.
Furthermore, occupant protection is a top concern of truck manufacturers. Vehicles are often designed with xe2x80x98crush zonesxe2x80x99 around the occupant to absorb the energy of a crash, while the occupied area of the vehicle stays relatively intact. The occupied area, namely, the cab, should thus be stiff relative to the rest of the vehicle, and particularly relative to the crush zones. Since day cab conversions have heretofore been relatively flimsy, day cab conversions may not have offered the level of occupant protection afforded by, e.g. a day cab that was originally designed as a day cab. It would be desirable if a day cab conversion were optimized to take maximum advantage of a vehicle""s crush zones, by being part of a system that controls the dissipation of energy incurred during a crash.
In a first embodiment, the invention is a conversion kit assembly for converting a modular truck sleeper/cab including a sleeper truck cab and a modular sleeper into a day cab. The sleeper truck cab includes a floor having a rear sill, two laterally spaced walls, and a roof, with each of the walls having a B-pillar at a rearward end of the sleeper truck cab. The B-pillars are coupled together at their upper ends by the roof and their lower ends by a lower member such as a lower panel or a rear sill, such that the rearward end of the sleeper truck cab may be substantially square. The sleeper truck cab further has a plurality of attachment points at the rearward end for attaching the modular sleeper.
The conversion kit includes a closeoff panel assembly comprising a frame sub-assembly and an outer panel welded to the frame, the closeoff panel assembly being attached to the sleeper truck cab by fasteners disposed at locations corresponding to at least some of a plurality of existing attachment points. First and second reinforcement members connect the closeoff panel assembly to the B-pillars of the sleeper truck cab, and third and fourth reinforcement members connect the closeoff panel assembly to the lower member of the sleeper truck cab, to distribute loads from the closeoff panel to the sleeper truck cab, and thence to the vehicle chassis.
In a second embodiment, the invention is a method of converting a modular truck sleeper/cab to a day cab. A modular truck sleeper/cab having a modular sleeper fastened to a rearward end of a sleeper truck cab described previously in the first embodiment may be provided with a first plurality of fasteners at a plurality of predetermined locations. The first plurality of fasteners, which connects the modular sleeper to the sleeper truck cab, are removed. The modular sleeper may be removed from the sleeper truck cab thereby creating a rearward opening at rearward end of sleeper truck cab. A closeoff panel assembly may be provided to close the rearward opening created by removal of the modular sleeper from the sleeper truck cab. The closeoff panel assembly may be fastened to the sleeper truck cab with a second plurality of fasteners in the plurality of predetermined locations to close the rearward opening whereby the sleeper truck cab has the appearance of a day cab. The closeoff panel assembly may be connected to B-pillars of the sleeper truck cab with first and second reinforcement members. The closeoff panel assembly may be connected to a lower member such as a lower panel or a rear sill of the sleeper truck cab with third and fourth reinforcement members. Loads are distributed from the closeoff panel assembly to the sleeper truck cab by the reinforcement members.